There is the so-called flip-chip process as one of mounting techniques for semiconductor chips. In the flip-chip process, protrusive electrodes are formed on the surface of a semiconductor chip, and the protrusive electrodes are directly connected to electrode pads on a substrate.
In a flip-chip package, a resin 4 is filled into a gap between a semiconductor chip 1 and a substrate 2 to reinforce a connecting portion 3 therebetween in order to prevent stresses, which are generated due to the difference in thermal expansion coefficient between the semiconductor chip 1 and the substrate 2, from being concentrated on the connecting portion 3 and from damaging the connecting portion 3. Such a process is called an underfilling process (see FIG. 1).
The underfilling process is carried out by applying a liquid resin along an outer periphery of the semiconductor chip, filling the resin into a gap between the semiconductor chip and the substrate by utilizing a capillary action, and then heating the filled resin in, e.g., an oven to cure the resin.
In the underfilling process, a change in viscosity of the resin material with the lapse of time has to be taken into consideration. The reason is that, when the viscosity increases, an ejection amount of the liquid material through a material ejection port is reduced and the capillary action is insufficiently developed, thus giving rise to a problem that the liquid material is not filled in a proper amount into the gap. In the case of some material causing a large change in viscosity, the ejection amount is reduced, e.g., 10% or more after the lapse of six hours. It is hence required to compensate for the change in the ejection amount, which is caused depending on the viscosity change with the lapse of time.
Generally, a dispenser is used to fill the resin material in the underfilling process. One type of such a dispenser is a jet dispenser that ejects small droplets of the liquid material in a jet stream from a nozzle.
A method of carrying out the underfilling process by using the jet dispenser is disclosed in Japanese Patent Laid-Open Publication No. 2004-344883 (Patent Document 1), for example. In more detail, Patent Document 1 discloses a method for ejecting a viscous material onto a substrate by using a jet dispenser, the method including the steps of preparing a total volume of the viscous material to be ejected and a length over which the total volume of the viscous material is to be ejected, performing an operation to apply a plurality of viscous material droplets onto a weight gauge, generating a feedback signal representative of the weight of the plural viscous material droplets applied onto the weight gauge, and determining a maximum relative speed between the dispenser and the substrate such that the total volume of the viscous material is ejected over the aforementioned length.
The method disclosed in Patent Document 1 further includes the steps of determining respective volumes of the liquid material droplets, determining a total number of droplets required to provide a volume that is substantially equal to the aforementioned total volume, determining a distance between the droplets, which distance is required to substantially evenly distribute the viscous material droplets over the aforementioned length, and determining a rate value at which the viscous material droplets are ejected from the dispenser in order to eject the total volume of viscous material over the aforementioned length at a maximum relative speed.